1. Field of the Invention
The present invention relates to a remote module control system for controlling, through a switching system, a module which is disposed at a place remote from the switching system and accommodates a plurality of line/trunk circuits, and a control method thereof.
2. Description of the Related Art
For accommodating a plurality of subscriber's terminals located at a place remote (remote place) from a place where a switching system is arranged, employed is a mode of disposing a module which accommodates each subscriber's terminal at the remote place and connecting the module (this module will be referred to as a remote module hereinafter) and the switching system by a predetermined interface to accommodate each subscriber's terminal in the switching system. FIG. 5 is a block diagram showing structure of a system which accommodates a subscriber's terminal at a remote place by the control of such a remote control module. With reference to FIG. 5, a subscriber's terminal 300 arranged at a remote place is accommodated in a remote module 200 disposed at the remote place, and the remote module 200 and a switching system 100 are connected with each other through a predetermined interface.
The remote module 200 includes an interface circuit (INT circuit) 510 for the connection with the switching system 100 and also includes, in one-to-one correspondence to each subscriber's terminal 300, a line/trunk circuit (L/T circuit) 520 which accommodates the subscriber's terminal 300.
The switching system 100 includes a time-division switch 120 for conducting switched connection, an L/T circuit 140 for accommodating a subscriber's terminal (not shown) and a central processor 110 for controlling the time-division switch 120 and the L/T circuit 140 and also includes, in one-to-one correspondence to each remote module 200, an INT circuit 530 for the connection with the remote module 200. The central processor 110 also controls the L/T circuit 520 of the remote module 200 through the INT circuit 530.
In a conventional remote module control method, control of each L/T circuit 520 of the remote module 200 from the central processor 110 is realized by the reception and transmission of signals between the central processor 110 and the L/T circuit 520 through the INT circuit 530 and the INT circuit 510 of the remote module 200. In other words, this is the same procedure as that for controlling the L/T circuit 140 of the switching system 100 which accommodates a subscriber's terminal.
FIG. 6 is a sequence diagram showing operation according to a remote module control method by a conventional system. With reference to FIG. 6, in a case of data writing to the L/T circuit 520 of the remote module 200 from the central processor 110 of the switching system 100, the central processor 110, in order to confirm data-writability/data-unwritability of the L/T circuit 520, first scans the L/T circuit 520 for checking writability/unwritability through the INT circuit 530 and the INT circuit 510 (Step 601).
When it is confirmed by the scanning at Step 601 that the L/T circuit 520 is data-writable, the central processor 110 transfers data to the L/T circuit 520 through the INT circuit 530 and the INT circuit 510 (Step 602). Upon reception of the data, the L/T circuit 520 checks normality of the received data and notifies the central processor 110 of the result of the check through the INT circuit 510 and the INT circuit 530 (Step 603). When the check result shows normality of the received data, the central processor 110 finishes the data writing processing. On the other hand, when the result shows abnormality of the received data, processing will be repeated starting at Step 601.
For reading data from the L/T circuit 520 of the remote module 200, the central processor 110 first scans the L/T circuit 520 through the INT circuit 530 and the INT circuit 510 in order to confirm existence/non-existence of data to be read from the L/T circuit 520 (Step 604).
When it is confirmed by the scanning at Step 604 that data to be read exists in the L/T circuit 520, the central processor 110 reads the data from the L/T circuit 520 through the INT circuit 530 and the INT circuit 510 (Step 605). After the reception of the data, the central processor 110 checks normality of the received data and notifies the L/T circuit 520 of the result of the check through the INT circuit 530 and the INT circuit 510 (Step 606) to finish the reading processing.
The above-described conventional remote module control method, however, has a shortcoming that because a central processor of a switching system directly controls a line/trunk circuit of a remote module, a transmission delay of an interface circuit or a line increases a latency of the central processor to reduce a processing capacity.
In a case of the operation shown in FIG. 6, for example, transmission delays T1 to T4 are generated at the respective operations.